Cochlear implant stimulation calibration

ABSTRACT

Cochlear implant systems can include a cochlear electrode and a stimulator in electrical communication with the cochlear electrode. The stimulator can be in communication with a controller, which is in communication with a testing circuit and a switching network. The stimulator can include a plurality of source elements. The controller can control the switching network to place the plurality of source elements into communication with the testing circuit. The controller can further cause one of the plurality of source elements to emit an electrical current and can determine an amount of electrical current emitted from the source element using the testing circuit. The controller can compare the determined amount of electrical current emitted by the source element with a prescribed current. The controller can adjust the output of each of the plurality of source elements based on the determined amount of electrical current emitted by the stimulator.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.17/109,305, filed Dec. 2, 2020, the content of which is herebyincorporated by reference.

BACKGROUND

A cochlear implant is an electronic device that may be at leastpartially implanted surgically into the cochlea, the hearing organ ofthe inner ear, to provide improved hearing to a patient. Cochlearimplants may include components that are worn externally by the patientand components that are implanted internally in the patient.

Cochlear implants may stimulate the cochlear tissue using electricalsignals. Accuracy and precision of the electrical signals used tostimulate the cochlear nerve may be desired to ensure accurate andprecise representations of sound. A lack of accuracy and precision ofthe electrical signals may not only lead to a lack of accuracy andprecision of the representations of sound, but may also lead toundesired and unexpected charge accumulation within the tissue. This cancause damage to the cochlear tissue and/or implanted components.Cochlear implants may be calibrated before they are implanted internallyin the patient, but may lose accuracy and precision after they have beenimplanted.

SUMMARY

Some aspects of the disclosure are generally directed toward cochlearimplant systems. In some examples, a cochlear implant system can includea cochlear electrode comprising a plurality of contact electrode. Thecochlear implant system can further include a stimulator in electricalcommunication with the cochlear electrode with the stimulator includinga plurality of source element. Each of the plurality of source elementcan be in electrical communication with a corresponding one of theplurality of contact electrodes of the cochlear electrode. The cochlearimplant system can further include an input source configured to receivea stimulus signal and generate an input signal based on the receivedstimulus signal. The cochlear implant system can also include a signalprocessor in communication with the stimulator and the input source withthe signal processor being programmed with a transfer function and beingconfigured to receive the input signal form the input source. The signalprocessor can output a stimulation signal to the stimulator based on thereceived input signal and the transfer function. The cochlear implantsystem can further include a testing circuit and a switching networkwith the switching network configured to selectively place each of theplurality of source elements into electrical communication with thetesting circuit. The cochlear implant system can also include acontroller in communication with the stimulator, the testing circuit,and the switching network. The controller can be configured to controlthe switching network to place one of the plurality of source elementinto communication with the testing circuit. The controller can furtherbe configured to cause the stimulator to emit an electrical current fromthe one of the plurality of source elements in communication with thetesting circuit. The controller can also be configured to determine anamount of electrical current emitted from the one of the plurality ofsource elements via the testing circuit. The controlled can also beconfigured to adjust the output of the one of the plurality of sourceelement based on the determined amount of electrical current.

Some other aspects of the present disclosure are generally related tomethods of calibrating current flow in a cochlear implant system. Insome examples, a method of calibrating current flow in a cochlearimplant system can include manipulating a switching network to positiona first source element, corresponding to one of a plurality of contactelectrodes of a cochlear electrode, into communication with a testingcircuit. The method can further include providing an electrical currentfrom the first source element to the testing circuit and determining anamount of electrical current provided by the first source element viathe testing circuit. The method can also include adjusting the output ofthe first source element based on the determined amount of electricalcurrent.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic illustration of a fully implantable cochlearimplant system.

FIG. 2 shows an embodiment of a fully implantable cochlear implant.

FIG. 3 illustrates an embodiments of an exemplary middle ear sensor foruse in conjunction with anatomical features of a patient.

FIG. 4 is a schematic diagram illustrating an exemplary implantablesystem including an acoustic stimulator.

FIG. 5A is a high-level electrical schematic showing communicationbetween the implantable battery and/or communication module and thesignal processor.

FIG. 5B illustrates an exemplary schematic diagram illustrating acochlear electrode having a plurality of contact electrodes and fixedlyor detachably connected to an electrical stimulator.

FIG. 6A shows an exemplary schematic illustration of processor andstimulator combined into a single housing.

FIG. 6B shows a simplified cross-sectional view of theprocessor/stimulator shown in FIG. 6A taken along lines B-B.

FIG. 7A is a high-level electrical schematic showing communicationsbetween various components of a cochlear implant system for a singlecontact electrode including a testing circuit.

FIG. 7B is an example embodiment of the testing circuit of FIG. 7A.

FIG. 7C is an alternative embodiment of the testing circuit of FIG. 7A.

FIG. 7D shows an example source element including a signal generationDAC and a calibration DAC.

FIG. 8 is a high-level electrical schematic showing communicationsbetween various components of a cochlear implant system for multiplecontact electrodes including a testing circuit.

FIG. 9 shows a schematic illustration of an example fully implantablecochlear implant system with an external device for programming.

FIG. 10 is an example adjustment process using a controller for acochlear implant system.

FIG. 11 is an alternative example adjustment process using a controllerfor a cochlear implant system.

DETAILED DESCRIPTION

FIG. 1 shows a schematic illustration of a fully implantable cochlearimplant system. The system of FIG. 1 includes a middle ear sensor 110 incommunication with a signal processor 120. The middle ear sensor 110 canbe configured to detect incoming sound waves, for example, using the earstructure of a patient. The signal processor 120 can be configured toreceive a signal from the middle ear sensor 110 and produce an outputsignal based thereon. For example, the signal processor 120 can beprogrammed with instructions to output a certain signal based on areceived signal. In some embodiments, the output of the signal processor120 can be calculated using an equation based on received input signals.Alternatively, in some embodiments, the output of the signal processor120 can be based on a lookup table or other programmed (e.g., in memory)correspondence between the input signal from the middle ear sensor 110and the output signal. While not necessarily based explicitly on afunction, the relationship between the input to the signal processor 120(e.g., from the middle ear sensor 110) and the output of the signalprocessor 120 is referred to as the transfer function of the signalprocessor 120.

In various examples, the signal processor 120 can comprise any varietyof components, for example, digital and/or analog processing components.In some embodiments, signal processor 120 comprises a digital signalprocessor, one or more microprocessors, microcontrollers, applicationspecific integrated circuits (ASICs) or the like. Supporting circuitryfor one or more such components can also be included as a part of thesignal processor. In some embodiments, the signal processor can includeor otherwise communicate with a memory containing programming foroperating one or more components. Additionally or alternatively, in someembodiments, the signal processor can include one or more additionalcomponents. For example, in some embodiments, signal processor caninclude an embedded microphone or other sensor configured to detectincoming sound waves.

The system of FIG. 1 further includes a cochlear electrode 116 implantedinto the cochlear tissues of a patient. The cochlear electrode 116 is inelectrical communication with an electrical stimulator 130, which can beconfigured to provide electrical signals to the cochlear electrode 116in response to input signals received by the electrical stimulator 130.In some examples, the cochlear electrode 116 is fixedly attached to theelectrical stimulator 130. In other examples, the cochlear electrode 116is removably attached to the electrical stimulator 130. As shown, theelectrical stimulator 130 is in communication with the signal processor120. In some embodiments, the electrical stimulator 130 provideselectrical signals to the cochlear electrode 116 based on output signalsfrom the signal processor 120.

In various embodiments, the cochlear electrode 116 can include anynumber of contact electrodes in electrical contact with different partsof the cochlear tissue. In such embodiments, the electrical stimulator130 can be configured to provide electrical signals to any number ofsuch contact electrodes to stimulate the cochlear tissue. For example,in some embodiments, the electrical stimulator 130 is configured toactivate different contact electrodes or combinations of contactelectrodes of the cochlear electrode 116 in response to different inputsignals received from the signal processor 120. This can help thepatient differentiate between different input signals.

During exemplary operation, the middle ear sensor 110 detects audiosignals, for example, using features of the patient's ear anatomy asdescribed elsewhere herein and in U.S. Patent Publication No.2013/0018216, which is hereby incorporated by reference in its entirety.The signal processor 120 can receive such signals from the middle earsensor 110 and produce an output to the electrical stimulator 130 basedon the transfer function of the signal processor 120. The electricalstimulator 130 can then stimulate one or more contact electrodes of thecochlear electrode 116 based on the received signals from the signalprocessor 120.

Referring to FIG. 2 , an embodiment of a fully-implantable cochlearimplant is shown. The device in this embodiment includes a processor 220(e.g., signal processor), a sensor 210, a first lead 270 connecting thesensor 210 to the processor 220, and a combination lead 280 attached tothe processor 220, wherein combination lead 280 contains both a groundelectrode 217 and a cochlear electrode 216. The illustrated processor220 includes a housing 202, a coil 208, first female receptacle 271 andsecond female receptacle 281 for insertion of the leads 270 and 280,respectively.

In some embodiments, coil 208 can receive power and/or data from anexternal device, for instance, including a transmission coil (notshown). Some such examples are described in U.S. Patent Publication No.2013/0018216, which is incorporated by reference. In other examples,processor 220 is configured to receive power and/or data from othersources, such as an implantable battery and/or communication module asshown in FIG. 1 . Such battery and/or communication module can beimplanted, for example, into the pectoral region of the patient in orderto provide adequate room for larger equipment (e.g., a relatively largebattery) for prolonged operation (e.g., longer battery life).Additionally, in the event a battery needs eventual replacement, areplacement procedure in the patient's pectoral region can be performedseveral times without certain vascularization issues that can arise nearthe location of the cochlear implant. For example, in some cases,repeated procedures (e.g., battery replacement) near the cochlearimplant can result in a decreased ability for the skin in the region toheal after a procedure. Placing a replaceable component such as abattery in the pectoral region can facilitate replacement procedureswith reduced risk for such issues.

FIG. 3 illustrates embodiments of an exemplary middle ear sensor for usein conjunction with anatomical features of a patient. Referring to FIG.3 , an embodiment of the sensor 310 of a fully-implantable cochlearimplant is shown. Also shown are portions of the subject's anatomy,which includes, if the subject is anatomically normal, at least themalleus 322, incus 324, and stapes 326 of the middle ear 328, and thecochlea 348, oval window 346, and round window 344 of the inner ear 342.Here, the sensor 310 is touching the incus 324. The sensor 310 caninclude a sensor such as described in U.S. Patent Publication No.2013/0018216, which is incorporated by reference. Further, although notshown in a drawing, the sensor 310 may be in operative contact with thetympanic membrane or the stapes, or any combination of the tympanicmembrane, malleus 322, incus 324, or stapes 326.

FIG. 3 illustrates an exemplary middle ear sensor for use with systemsdescribed herein. However, other middle ear sensors can be used, such assensors using microphones or other sensors capable of receiving an inputcorresponding to detected sound and outputting a corresponding signal tothe signal processor. Additionally or alternatively, systems can includeother sensors configured to output a signal representative of soundreceived at or near a user's ear, such as a microphone or other acousticpickup located in the user's outer ear or implanted under the user'sskin. Such devices may function as an input source, for example, to thesignal processor such that the signal processor receives an input signalfrom the input source and generates and output one or more stimulationsignals according to the received input signal and the signal processortransfer function. Additionally or alternatively, systems can includeother types of sensors, such as inner ear sensors. Some exampleconfigurations of such systems and other sensor arrangements aredescribed in PCT patent application No. PCT/US20/19166, filed Feb. 21,2020, which is assigned to the assignee of the instant application andis incorporated by reference.

Referring back to FIG. 1 , the signal processor 120 is shown as being incommunication with the middle ear sensor 110, the electrical stimulator130, and the implantable battery and/or communication module 140. Asdescribed elsewhere herein, the signal processor 120 can receive inputsignals from the middle ear sensor 110 and/or other input source(s) andoutput signals to the electrical stimulator 130 for stimulating thecochlear electrode 116. The signal processor 120 can receive data (e.g.,processing data establishing or updating the transfer function of thesignal processor 120) and/or power from the implantable battery and/orcommunication module 140.

In some embodiments, the implantable battery and/or communication module140 can communicate with one or more external components, such as aprogrammer 100 and/or a battery charger 102. The battery charger 102 canwirelessly charge the battery in the implantable battery and/orcommunication module 140 when brought into proximity with theimplantable battery and/or communication module 140 in the pectoralregion of the patient. Such charging can be accomplished, for example,using inductive charging. The programmer 100 can be configured towirelessly communicate with the implantable battery and/or communicationmodule 140 via any appropriate wireless communication technology, suchas Bluetooth, Wi-Fi, and the like. In some examples, the programmer 100can be used to update the system firmware and/or software. In anexemplary operation, the programmer 100 can be used to communicate anupdated signal processor 120 transfer function to the implantablebattery and/or communication module 140. In various embodiments, theprogrammer 100 and charger 102 can be separate devices or can beintegrated into a single device.

In the illustrated example of FIG. 1 , the signal processor 120 isconnected to the middle ear sensor 110 via lead 170. In someembodiments, lead 170 can provide communication between the signalprocessor 120 and the middle ear sensor 110. In some embodiments, lead170 can include a plurality of isolated conductors providing a pluralityof communication channels between the middle ear sensor 110 and thesignal processor 120. The lead 170 can include a coating such as anelectrically insulating sheath to minimize any conduction of electricalsignals to the body of the patient. In various embodiments, one or morecommunication leads can be detachable such that communication betweentwo components can be disconnected in order to electrically and/ormechanically separate such components. For instance, in someembodiments, lead 170 includes a detachable connector 171. Detachableconnector 171 can facilitate decoupling of the signal processor 120 andmiddle ear sensor 110. Example detachable connectors are described inPCT patent application No. PCT/US20/19166, which is incorporated byreference. For example, with reference to FIG. 1 , in some embodiments,lead 170 can include a first lead extending from the middle ear sensor110 having one of a male or a female connector and a second leadextending from the signal processor 120 having the other of the male orfemale connector. The first and second leads can be connected atdetachable connector 171 in order to facilitate communication betweenthe middle ear sensor 110 and the signal processor 120.

In other examples, a part of the detachable connector 171 can beintegrated into one of the middle ear sensor 110 and the signalprocessor 120. For example, in an exemplary embodiment, the signalprocessor 120 can include a female connector integrated into a housingof the signal processor 120. Lead 170 can extend fully from the middleear sensor 110 and terminate at a corresponding male connector forinserting into the female connector of the signal processor 120. Instill further embodiments, a lead (e.g., 170) can include connectors oneach end configured to detachably connect with connectors integratedinto each of the components in communication. For example, lead 170 caninclude two male connectors, two female connectors, or one male and onefemale connector for detachably connecting with corresponding connectorsintegral to the middle ear sensor 110 and the signal processor 120.Thus, lead 170 may include two or more detachable connectors.

Similar communication configurations can be established for detachableconnector 181 of lead 180 facilitating communication between the signalprocessor 120 and the stimulator 130 and for detachable connector 191 oflead 190 facilitating communication between the signal processor 120 andthe implantable battery and/or communication module 140. Leads (170,180, 190) can include pairs of leads having corresponding connectorsextending from each piece of communicating equipment, or connectors canbe built in to any one or more communicating components.

In such configurations, each of the electrical stimulator 130, signalprocessor 120, middle ear sensor 110, and battery and/or communicationmodule can each be enclosed in a housing, such as a hermetically sealedhousing comprising biocompatible materials. Such components can includefeedthroughs providing communication to internal components enclosed inthe housing. Feedthroughs can provide electrical communication to thecomponent via leads extending from the housing and/or connectorsintegrated into the components.

In a module configuration such as that shown in FIG. 1 , variouscomponents can be accessed (e.g., for upgrades, repair, replacement,etc.) individually from other components. For example, as signalprocessor 120 technology improves (e.g., improvements in size,processing speed, power consumption, etc.), the signal processor 120implanted as part of the system can be removed and replacedindependently of other components. In an exemplary procedure, animplanted signal processor 120 can be disconnected from the electricalstimulator 130 by disconnecting detachable connector 181, from themiddle ear sensor 110 by disconnecting detachable connector 171, andfrom the implantable battery and/or communication module 140 bydisconnecting detachable connector 191. Thus, the signal processor 120can be removed from the patient while other components such as theelectrical stimulator 130, cochlear electrode 116, middle ear sensor110, and battery and/or communication module can remain in place in thepatient.

After the old signal processor is removed, a new signal processor can beconnected to the electrical stimulator 130, middle ear sensor 110, andimplantable battery and/or communication module 140 via detachableconnectors 181, 171, and 191, respectively. Thus, the signal processor(e.g., 120) can be replaced, repaired, upgraded, or any combinationthereof, without affecting the other system components. This can reduce,among other things, the risk, complexity, duration, and recovery time ofsuch a procedure. In particular, the cochlear electrode 116 can be leftin place in the patient's cochlea while other system components can beadjusted, reducing trauma to the patient's cochlear tissue.

Such modularity of system components can be particularly advantageouswhen replacing a signal processor 120, such as described above.Processor technology continues to improve and will likely continue tomarkedly improve in the future, making the signal processor 120 a likelycandidate for significant upgrades and/or replacement during thepatient's lifetime. Additionally, in embodiments such as the embodimentshown in FIG. 1 , the signal processor 120 communicates with many systemcomponents. For example, as shown, the signal processor 120 is incommunication with each of the electrical stimulator 130, the middle earsensor 110, and the implantable battery and/or communication module 140.Detachably connecting such components with the signal processor 120(e.g., via detachable connectors 181, 171, and 191) enables replacementof the signal processor 120 without disturbing any other components.Thus, in the event of an available signal processor 120 upgrade and/or afailure of the signal processor 120, the signal processor 120 can bedisconnected from other system components and removed.

While many advantages exist for a replaceable signal processor 120, themodularity of other system components can be similarly advantageous, forexample, for upgrading any system component. Similarly, if a systemcomponent (e.g., the middle ear sensor 110) should fail, the componentcan be disconnected from the rest of the system (e.g., via detachableconnector 171) and replaced without disturbing the remaining systemcomponents. In another example, even a rechargeable battery included inthe implantable battery and/or communication module 140 may eventuallywear out and need replacement. The implantable battery and/orcommunication module 140 can be replaced or accessed (e.g., forreplacing the battery) without disturbing other system components.Further, as discussed elsewhere herein, when the implantable batteryand/or communication module 140 is implanted in the pectoral region ofthe patient, such as in the illustrated example, such a procedure canleave the patient's head untouched, eliminating unnecessarily frequentaccess beneath the skin.

While various components are described herein as being detachable, invarious embodiments, one or more components configured to communicatewith one another can be integrated into a single housing. For example,in some embodiments, signal processor 120 can be integrally formed withthe stimulator 130 and cochlear electrode 116. For example, in anexemplary embodiment, processing and stimulation circuitry of a signalprocessor 120 and stimulator 130 can be integrally formed as a singleunit in a housing coupled to a cochlear electrode. Cochlear electrodeand the signal processor/stimulator can be implanted during an initialprocedure and operate as a single unit.

In some embodiments, while the integral signalprocessor/stimulator/cochlear electrode component does not get removedfrom a patient due to potential damage to the cochlear tissue into whichthe cochlear electrode is implanted, system upgrades are still possible.For example, in some embodiments, a modular signal processor may beimplanted alongside the integral signal processor/stimulator componentand communicate therewith. In some such examples, the integral signalprocessor may include a built-in bypass to allow a later-implantedsignal processor to interface directly with the stimulator. Additionallyor alternatively, the modular signal processor can communicate with theintegral signal processor, which may be programmed with a unity transferfunction. Thus, in some such embodiments, signals from the modularsignal processor may be essentially passed through the integral signalprocessor unchanged so that the modular signal processor effectivelycontrols action of the integral stimulator. Thus, in variousembodiments, hardware and/or software solutions exist for upgrading anintegrally attached signal processor that may be difficult or dangerousto remove.

While often described herein as using an electrical stimulator tostimulate the patient's cochlear tissue via a cochlear electrode, insome examples, the system can additionally or alternatively include anacoustic stimulator. An acoustic stimulator can include, for example, atransducer (e.g., a piezoelectric transducer) configured to providemechanical stimulation to the patient's ear structure. In an exemplaryembodiment, the acoustic stimulator can be configured to stimulate oneor more portions of the patient's ossicular chain via amplifiedvibrations. Acoustic stimulators can include any appropriate acousticstimulators, such as those found in the ESTEEM™ implant (Envoy MedicalCorp., St. Paul, Minn.) or as described in U.S. Pat. Nos. 4,729,366,4,850,962, and 7,524,278, and U.S. Patent Publication No. 20100042183,each of which is incorporated herein by reference in its entirety.

FIG. 4 is a schematic diagram illustrating an exemplary implantablesystem including an acoustic stimulator. The acoustic stimulator can beimplanted proximate the patient's ossicular chain and can be incommunication with a signal processor via lead 194 and detachableconnector 195. The signal processor can behave as described elsewhereherein and can be configured to cause acoustic stimulation of theossicular chain via the acoustic stimulator in in response to inputsignals from the middle ear sensor according to a transfer function ofthe signal processor.

The acoustic stimulator of FIG. 4 can be used similarly to theelectrical stimulator as described elsewhere herein. For instance, anacoustic stimulator can be mechanically coupled to a patient's ossicularchain upon implanting the system and coupled to the signal processor vialead 194 and detachable connector 195. Similarly to systems describedelsewhere herein with respect to the electrical stimulator, if thesignal processor requires replacement or repair, the signal processorcan be disconnected from the acoustic stimulator (via detachableconnector 195) so that the signal processor can be removed withoutdisturbing the acoustic stimulator.

In general, systems incorporating an acoustic stimulator such as shownin FIG. 4 can operate in the same way as systems described elsewhereherein employing an electrical stimulator and cochlear electrode onlysubstituting electrical stimulation for acoustic stimulation.

Some systems can include a hybrid system comprising both an electricalstimulator and an acoustic stimulator in communication with the signalprocessor. In some such examples, the signal processor can be configuredto stimulate electrically and/or acoustically according to the transferfunction of the signal processor. In some examples, the type ofstimulation used can depend on the input signal received by the signalprocessor. For instance, in an exemplary embodiment, the frequencycontent of the input signal to the signal processor can dictate the typeof stimulation. In some cases, frequencies below a threshold frequencycould be represented using one of electrical and acoustic stimulationwhile frequencies above the threshold frequency could be representedusing the other of electrical and acoustic stimulation. Such a thresholdfrequency could be adjustable based on the hearing profile of thepatient. Using a limited range of frequencies can reduce the number offrequency domains, and thus the number of contact electrodes, on thecochlear electrode. In other examples, rather than a single thresholdfrequency defining which frequencies are stimulated electrically andacoustically, various frequencies can be stimulated both electricallyand acoustically. In some such examples, the relative amount ofelectrical and acoustic stimulation can be frequency-dependent. Asdescribed elsewhere herein, the signal processor transfer function canbe updated to meet the needs of the patient, including the electricaland acoustic stimulation profiles.

Additionally or alternatively, while many examples show a middle earsensor being in communication with an implanted signal processor, invarious embodiments, one or more additional or alternative input sourcescan be included. For instance, in some embodiments, a microphone can beimplanted under a user's skin and can be placed in communication withthe signal processor (e.g., via a detachable connector such as 171). Thesignal processor can receive input signals from the implanted microphoneand provide signals to the stimulator based on the received input signaland the signal processor transfer function. Additionally oralternatively, systems can include a middle ear sensor as an inputsource, wherein the middle ear sensor is configured to detect stimuli(e.g., pressure signals) from the wearer's inner ear (e.g., within thecochlear tissue).

With further reference to FIGS. 1 and 4 , in some examples, a system caninclude a shut-off controller 104, which can be configured to wirelesslystop an electrical stimulator 130 from stimulating the patient'scochlear tissue and/or an acoustic stimulator 150 from stimulating thepatient's ossicular chain. For example, if the system is malfunctioningor an uncomfortably loud input sound causes an undesirable level ofstimulation, the user may use the shut-off controller 104 to ceasestimulation from the stimulator 130. The shut-off controller 104 can beembodied in a variety of ways. For example, in some embodiments, theshut-off controller 104 can be integrated into other externalcomponents, such as the programmer 100. In some such examples, theprogrammer 100 includes a user interface by which a user can select anemergency shut-off feature to cease stimulation. Additionally oralternatively, the shut-off controller 104 can be embodied as a separatecomponent. This can be useful in situations in which the patient may nothave immediate access to the programmer 100. For example, the shut-offcontroller 104 can be implemented as a wearable component that thepatient can wear at all or most times, such as a ring, bracelet,necklace, or the like.

The shut-off controller 104 can communicate with the system in order tostop stimulation in a variety of ways. In some examples, the shut-offcontroller 104 comprises a magnet that is detectable by a sensor (e.g.,a Hall-Effect sensor) implanted in the patient, such as in the processorand/or the implantable battery and/or communication module 140. In somesuch embodiments, when the magnet is brought sufficiently close to thesensor, the system can stop stimulation of the cochlear tissue orossicular chain.

After the shut-off controller 104 is used to disable stimulation,stimulation can be re-enabled in one or more of a variety of ways. Forexample, in some embodiments, stimulation is re-enabled after apredetermined amount of time after it had been disabled. In otherexamples, the shut-off controller 104 can be used to re-enablestimulation. In some such examples, the patient brings the shut-offcontroller 104 within a first distance of a sensor (e.g., a magneticsensor) to disable stimulation, and then removes the shut-off controller104. Subsequently, once the patient brings the shut-off controller 104within a second distance of the sensor, stimulation can be re-enabled.In various embodiments, the first distance can be less than the seconddistance, equal to the second distance, or greater than the seconddistance. In still further embodiments, another device such as aseparate turn-on controller (not shown) or the programmer 100 can beused to re-enable stimulation. Any combination of such re-enabling ofstimulation can be used, such as alternatively using either theprogrammer 100 or the shut-off controller 104 to enable stimulation orcombining a minimum “off” time before any other methods can be used tore-enable stimulation.

In some embodiments, rather than entirely disable stimulation, otheractions can be taken, such as reducing the magnitude of stimulation. Forexample, in some embodiments, the shut-off sensor can be used to reducethe signal output by a predetermined amount (e.g., absolute amount,percentage, etc.). In other examples, the shut-off sensor can affect thetransfer function of the signal processor to reduce the magnitude ofstimulation in a customized way, such as according to frequency or otherparameter of an input signal (e.g., from the middle ear sensor).

In some examples, implantable battery and/or communication module can beused to provide power and/or data (e.g., processing instructions) toother system components via lead 190. Different challenges exist forcommunicating electrical signals through a patient's body. For example,safety standards can limit the amount of current that can safely flowthrough a patient's body (particularly DC current). Additionally, thepatient's body can act as an undesired signal path from component tocomponent (e.g., via contact with the housing or “can” of eachcomponent).

FIG. 5A is a high-level electrical schematic showing communicationbetween the implantable battery and/or communication module and thesignal processor. In the illustrated embodiment, the implantable batteryand/or communication module includes circuitry in communication withcircuitry in the signal processor. Communication between the circuitryin the implantable battery and/or communication module and the signalprocessor can be facilitated by a lead (190), represented by the leadtransfer function. The lead transfer function can include, for example,parasitic resistances and capacitances between the leads connecting theimplantable battery and/or communication module and the signal processorand the patient's body and/or between two or more conductors that makeup the lead (e.g., 191). Signals communicated from the circuitry of theimplantable battery and/or communication module to the circuitry in thesignal processor can include electrical power provided to operate and/orstimulate system components (e.g., the middle ear sensor, signalprocessor, electrical and/or acoustic stimulator, and/or cochlearelectrode) and/or data (e.g., processing data regarding the transferfunction of the signal processor).

Various systems and methods can be employed provide communicationbetween system components. Some examples of possible communicationtechniques are described in PCT patent application No. PCT/US20/19166,which is incorporated by reference. In some examples, data can becommunicated to the implantable battery and/or communication module froman external component, such as a programmer as shown in FIG. 1 . In anexemplary process, a programmer, such as a clinician's computer, can beused to communicate with a patient's fully implanted system via theimplantable battery and/or communication module, which can communicateinformation to other system components, such as via lead 190.

During such processes, a clinician can communicate with the signalprocessor, and, in some cases, with other components via the signalprocessor. For example, the clinician can cause the signal processor toactuate an electrical and/or an acoustic stimulator in various ways,such as using various electrical stimulation parameters, combinations ofactive contact electrodes, various acoustic stimulation parameters, andvarious combinations thereof. Varying the stimulation parameters in realtime can allow the clinician and patient to determine effectiveness ofdifferent stimulation techniques for the individual patient. Similarly,the clinician can communicate with the signal processor to updatetransfer function. For example, the clinician can repeatedly update thetransfer function signal processor while testing the efficacy of eachone on the individual patient. In some examples, combinations ofstimulation parameters and signal processor transfer functions can betested for customized system behavior for the individual patient.

In some embodiments, various internal properties of the system may betested. For instance, various impedance values, such as a sensorimpedance or a stimulator impedance can be tested such as described inU.S. Patent Publication No. 2015/0256945, entitled TRANSDUCER IMPEDANCEMEASUREMENT FOR HEARING AID, which is assigned to the assignee of theinstant application, the relevant portions of which are incorporated byreference herein.

As discussed elsewhere herein, the body of the patient provides anelectrical path between system components, such as the “can” of theimplantable battery and/or communication module and the “can” of thesignal processor. This path is represented in FIG. 5A by the flow paththrough R_(Body). Thus, the patient's body can provide undesirablesignal paths which can negatively impact communication betweencomponents. To address this, in some embodiments, operating circuitry ineach component can be substantially isolated from the component “can”and thus the patient's body. For example, as shown, resistance R_(Can)is positioned between the circuitry and the “can” of both theimplantable battery and/or communication module and the signalprocessor.

While being shown as R_(Can) in each of the implantable battery and/orcommunication module and the signal processor, it will be appreciatedthat the actual value of the resistance between the circuitry andrespective “can” of different elements is not necessarily equal.Additionally, Rcan need not include purely a resistance, but can includeother components, such as one or more capacitors, inductors, and thelike. That is, Rcan can represent an insulating circuit including anyvariety of components that act to increase the impedance betweencircuitry within a component and the “can” of the component. Thus,R_(Can) can represent an impedance between the operating circuitry of acomponent and the respective “can” and the patient's tissue. Isolatingthe circuitry from the “can” and the patient's body acts to similarlyisolate the circuitry from the “can” of other components, allowing eachcomponent to operate with reference to a substantially isolatedcomponent ground. This can eliminate undesired communication andinterference between system components and/or between system componentsand the patient's body.

For example, as described elsewhere herein, in some examples, anelectrical stimulator can provide an electrical stimulus to one or morecontact electrodes on a cochlear electrode implanted in a patient'scochlear tissue. FIG. 5B illustrates an exemplary schematic diagramillustrating a cochlear electrode having a plurality of contactelectrodes and fixedly or detachably connected to an electricalstimulator. As shown, the cochlear electrode 500 has four contactelectrodes 502, 504, 506, and 508, though it will be appreciated thatany number of contact electrodes is possible. As described elsewhereherein, the electrical stimulator can provide electrical signals to oneor more such contact electrodes in response to an output from the signalprocessor according to the transfer function thereof and a receivedinput signal.

Because each contact electrode 502-1008 is in contact with the patient'scochlear tissue, each is separated from the “can” of the electricalstimulator (as well as the “cans” of other system components) via theimpedance of the patient's tissue, shown as R_(Body). Thus, if thecircuitry within various system components did not have sufficientlyhigh impedance (e.g., Rcan) to the component “can”, electrical signalsmay stimulate undesired regions of the patient's cochlear tissue. Forinstance, stimulation intended for a particular contact electrode (e.g.,502) may lead to undesired stimulation of other contact electrodes(e.g., 504, 506, 508), reducing the overall efficacy of the system.Minimizing the conductive paths between system components (e.g., to thecontact electrodes of a cochlear electrode) due to the patient's body,such as by incorporating impedances between component circuitry and thecorresponding “can” via R_(Can), can therefore improve the ability toapply an electrical stimulus to only a desired portion of the patient'sbody.

It will be appreciated that the term R_(Body) is used herein togenerally represent the resistance and/or impedance of the patient'stissue between various components and does not refer to a specificvalue. Moreover, each depiction or R_(Body) in the figures does notnecessarily represent the same value of resistance and/or impedance asthe others.

While shown in several embodiments (e.g., FIGS. 1 and 4 ) as beingseparate components connected by a lead (e.g., lead 180), in someexamples, the processor (e.g., 120) and the stimulator (e.g., 130) canbe integrated into a single component, for example, within ahermetically sealed housing. FIG. 6A shows an exemplary schematicillustration of processor and stimulator combined into a single housing.In the example of FIG. 6A, the processor/stimulator 620 receives signalinputs from the sensor (e.g., a middle ear sensor) via lead 670 andpower from a battery (e.g., the implantable battery and/or communicationmodule) via lead 690. The processor/stimulator 620 can include headers622, 624 for receiving leads 670, 690, respectively.

The processor/stimulator 620 can be configured to receive an inputsignal from the sensor, process the received input signal according to atransfer function, and output a stimulation signal via electrode 626.Electrode 626 can include one or more contact electrodes (e.g., 628) incontact with a wearer's cochlear tissue to provide electricalstimulation thereto, for example, as described with respect to FIG. 5B.

The processor/stimulator 620 of FIG. 6 includes a return electrode 630for providing a return path (e.g., 632) for stimulation signals emittedfrom electrode 626. The return electrode 630 can be electrically coupledto a ground portion of circuitry within the processor/stimulator 620 tocomplete a circuit comprising circuitry within the processor/stimulator620, the electrode 626, the wearer's cochlear tissue, and ground. Insome examples, the return electrode 630 comprises an electricallyconductive material in electrical communication with circuitry insidethe processor/stimulator 620, while the rest of the housing of theprocessor/stimulator 620 is generally not electrically coupled tointernal circuitry.

In some embodiments, the return electrode 630 and the housing of theprocessor/stimulator 620 comprise electrically conductive materials. Forinstance, in some examples, the housing comprises titanium while thereturn electrode 630 comprises platinum or a platinum alloy. Header 624can generally include a non-conductive biocompatible material, such as abiocompatible polymer. The non-conductive header 624 can provideisolation between the return electrode 630 and the conductive housing ofthe processor/stimulator 620.

While shown in FIG. 6A as being positioned in the power header 624 ofthe processor/stimulator 620, in general, the return electrode 630 canbe positioned anywhere on the exterior surface of theprocessor/stimulator 620. In some examples, one or more redundant returnelectrodes can be included, for example, at or near the interface of thehousing and the electrode 626. In some examples, a return electrode canbe positioned on a proximal end of the electrode 626 itself. In someembodiments having a plurality of return electrodes (e.g., returnelectrode 630 and a return electrode on the proximal end of electrode626), a switch can be used to select which return electrode is used.Additionally or alternatively, a plurality of return electrodes can beused simultaneously.

FIG. 6B shows a simplified cross-sectional view of theprocessor/stimulator shown in FIG. 6A taken along lines B-B. As shown inFIG. 6B, processor/stimulator 620 includes a housing having a first side619 and a second side 621 and a return electrode 630 embedded in thehousing. Return electrode 630 can comprise a conductive materialsuitable for contact with a wearer's tissue, such as platinum. In theillustrated example, the return electrode 630 wraps around to both sidesof the housing of the processor/stimulator 620 so that the returnelectrode 630 is coupled to the outer surface of the housing on thefirst side 619 and the second side 621.

This can facilitate implanting onto either side of a wearer's anatomy,since in some cases, only one side of the processor/stimulatorelectrically contacts conductive tissue of the wearer while the otherside contacts, for instance, the skull of the wearer, and does noteasily provide the return path (e.g., 632). Thus, a singleprocessor/stimulator design can be implanted in either side of awearer's anatomy while providing an adequate return path via a returnelectrode 630.

In various examples, the return electrode 630 can extend around aperimeter edge of the processor/stimulator 620, as shown in FIG. 6B. Inother examples, the return electrode 630 can include sections on eitherside of the housing and can be connected to one another internallywithin the housing rather than via a wrap-around contact. Additionally,while shown as being embedded in the housing of the processor/stimulator620, in some examples, return electrode 630 can protrude outwardly fromthe housing. Return electrode 630 can generally be any of a variety ofshapes and sizes while including an electrical contact section onopposing sides of the housing to provide usability on either side of awearer's anatomy. In other embodiments, return electrode can bepositioned only one side of the housing for a customized right-side orleft-side implementation.

As described elsewhere herein, in various embodiments, the processorgenerally receives an input signal, processes the signal, and generatesa stimulation signal, which can be applied via an integrated stimulator(e.g., via a processor/stimulator such as in FIGS. 6A and 6B) or aseparate stimulator in communication with the processor (e.g., as shownin FIGS. 1 and 4 ). In some such embodiments, the input signal receivedvia the signal processor is generated by an implantable sensor, such asa middle ear sensor (e.g., as described with respect to FIGS. 4 and 5 ).

However, such sensors often measure or otherwise receive some stimulusthat is converted into an output that is read and processed by thesignal processor. For example, some middle ear sensors may produce adifferent output signal for a given stimulus depending on a variety offactors, such as variability in a wearer's inner-ear anatomy and motion.Thus, the output of a sensor for a given input may be not predictablewhile designing a system, especially across a range of frequenciesand/or magnitudes.

It can be desirable to ensure the applied stimulation signal is acorrect interpretation of a prescribed signal for accuracy and safetyreasons. For example, for a given prescribed current to be applied viaan electrode, the actual applied current may depart from the prescribedcurrent. This can be due to various factors, such as electronicsimprecisely calibrated, the behavior of electronics over time, andvariability driven mismatches between various electronic components.However, it can be desirable to ensure electrical pulses generated bythe cochlear implant system are charge-balanced. Charge-balanced meansthat the amount of charge sourced to the wearer's tissue is the sameamount of charge sunk as delivered from the tissue over time. Forexample, to balance charge applied to patient tissue, a first current(e.g., in the form of pulses) put into the tissue via contact electrodesfor an amount of time would be the same magnitude as a second currenttaken out of the tissue via the contact electrodes for the same amountof time. Discrepancies between a prescribed current that the systembelieves is being sourced/sunk and the actual current being sourced/sunkcan result in unexpected and undetected charge accumulation over time.Such charge accumulation can cause damage to the wearer's tissue and/orthe implanted electronics and/or the deterioration of the interfacebetween the electrode and the tissue and/or fluid.

FIG. 7A is a high-level electrical schematic showing communicationsbetween a source element 710, a switch 715, a controller 700, a testingcircuit 720, and a contact electrode 730. In the illustrated embodiment,the switch 715 can selectively connect the source element 710 witheither of the testing circuit 720 or the contact electrode 730. Byconnecting the source element 710 to either the testing circuit 720 orthe contact electrode, current can flow from the source element 710 toeither of the testing circuit 720 or the contact electrode 730. As shownby the broken line in FIG. 7A, in some embodiments, a current can flowthrough the testing circuit 720 and to the contact electrode 730. Theswitch 715 can be any type of switch (e.g. transistor), and in someexamples more than one switch can be used. In some embodiments, theswitch 715 is controlled by the controller 700.

In various examples, controller 700 includes one or more processors,such as one or more digital signal processors and/or microprocessors.Additionally or alternatively, controller 700 can include one or moremicrocontrollers, application specific integrated circuits (ASICs) orthe like. In some embodiments, the controller 700 can include orotherwise communicate with a memory containing programming for operatingone or more components.

In some examples, source element 710 of FIG. 7A can include a currentsource and/or a current sink. As a current source, the source element710 can provide (e.g. source) a current to contact electrode 730 and/ortesting circuit 720. As a current sink, the source element 710 canreceive (e.g. sink) current which has traveled through the contactelectrode and/or the testing circuit. Current sources and/or sinks canbe provided via, for example, one or more current source or sinkintegrated circuits or other appropriate arrangement of one or morecomponents configured to source or sink current as would be understoodby a person having ordinary skill in the art. In various embodiments,source element 710 can source or sink current, for example, asprescribed by controller 700, which can provide a signal to the sourceelement 710 to control an amount of current sourced or sunk thereby.Unless specified otherwise, descriptions of embodiments herein in whicha source element (e.g., 710) provides a current (e.g., to contactelectrode 730) can similarly describe times or embodiments in which asource element sinks current. In various examples, a source element(e.g., 710) can “provide” positive or negative current to a contactelectrode, acting as a current source or a sink.

In some embodiments, current can originate from a power source andultimately return to the power source using the source element 710 as acurrent source and/or current sink. In some such embodiments, a circuitis formed where current flows from the power source through the sourceelement 710, through to the contact electrode 730 and/or testing circuit720, back through the source element 710, and back to the power source.During example stimulation, current from the source element 710 can flowthrough contract electrode 730 via switch 715, through a wearer'stissue, and return to a return electrode (e.g., return electrode 630 viapath 632 in FIG. 6 ).

As described elsewhere herein, the source element 710 can be included aspart of a stimulator (e.g. 130 and 150). In some embodiments, the sourceelement 710 comprises a digital to analog converter (DAC) which canconvert digital signals to analog signals. For example, in FIG. 7A, thesource element 710 is in communication with controller 700. In someexamples, controller 700 is part of a signal processor (e.g. 120), whichcan send a digital stimulation signal to the source element 710. In somesuch examples, the DAC of the source element 710 can convert the digitalsignal to an analog signal and provide the converted signal to thecontact electrode 730 or to another element that outputs a current tothe contact electrode 730 based on the received analog signal from theDAC. For instance, in some embodiments, such a DAC can be configured tooutput an analog signal (e.g., an analog voltage) to one or more currentsource or sink components in order to source or sink current via thecontact electrode based on the received digital signal from thecontroller 700. In general, the digital stimulation signal sent by thesignal processor to the source element 710 can comprise an amount ofcurrent to be delivered to the contact electrode, and can control anamount of current provided therefrom over time.

The DAC of the source element 710, can convert the digital stimulationsignal into an analog signal using a number of bits. In someembodiments, the least significant bits (LSB's) of the digital signalcan be considered trim bits which can be used to fine-tune the amount ofcurrent delivered to the contact electrode. In various embodiments anynumber of bits can be used to provide a stimulation signal. For example,in some embodiments, the stimulation signal provided to the DAC of thesource element 710 can include at least six bits of precision. In somesuch embodiments, the DAC can have seven, eight, nine, ten, eleven, ormore bits of precision. By using more bits, the source element 710 canhave a higher output precision of the digital input signal. Forinstance, in some examples, using by using 8 bits for the DAC (sourceelement 710), up to 256 distinct levels of current to the contactelectrode 730 can be output or otherwise initiated by the DAC via theanalog signal provided by the DAC. This can allow for more accuratestimulation by the contact electrode 730.

However, even with generally accurate stimulation, in some examples, thesource element 710 can deliver signals and currents to the contactelectrode which do not match the desired current. Further, in someembodiments, the source element 710 can source (e.g. deliver) morecurrent to the contact electrode 730 than it sinks (e.g. receives) fromthe contact electrode. An imbalance in current sourced and sunk bysource element 710 to the contact electrode can lead to accumulatedelectrical charge in the wearer's tissue and/or across the electrodeinterface, which can cause damage to the wearer (e.g., including damageto the cochlear tissue) and/or damage to the electrode(s) implantedtherein. It can thus be desirable to have the same amount of electricalcharge sourced to the contact electrode 730 by source element 710 assunk by source element 710.

While in some embodiments, the source element 710 including the DAC iscalibrated/programmed to be as accurate as possible when it ismanufactured, over time, it can become less accurate due to variousreasons (e.g. drift). For example, source element 710 can include bothp-channel metal oxide semiconductor devices (PMOS) and n-channel metaloxide semiconductors (NMOS) devices. PMOS and NMOS devices do not behavethe same way over time and may not track each other. The disparity inbehavior can result in inaccuracies in the prescribed current fromsource element 710. In such cases, even when the prescribed amount ofcurrent to be sourced/sunk should in theory result in a net-zero chargeaccumulation, inaccurate current application can lead to the totalcharge provided to the contact electrode 730 being different thandesired and can lead to undesired charge accumulation over time.Accordingly, it can be advantageous to be able to calibrate/programoperation of the source element after it has been implanted.

In FIG. 7A, testing circuit 720 can be put into communication withsource element 710 by switch 715. In some embodiments, testing circuitcan be configured to determine a current being sourced from or sunk tothe source element 710. FIGS. 7B and 7C show example implementations ofa testing circuit for determining a current provided by the sourceelement. In the embodiment of FIG. 7B, testing circuit 722 includes aprecision load 732, for example, a precision resistor or otherimpedance. The precision load 732 can be any type of impedance, howeverin some embodiments the precision load 732 comprises a resistor.Further, the precision load 732 can have any value of impedance, but insome embodiments, the value of impedance is a known quantity. In someexamples, the precision load 732 is mounted to a circuit board. Testingcircuit 722 can also include a way to measure the voltage across theprecision load 732 such as a voltmeter. In some embodiments, testingcircuit 722 can include an analog to digital converter (ADC) which canconvert analog signals (e.g. voltages) to digital representations of theanalog signals. In some such examples, such digital signal can beprovided to the controller 700 representing the voltage drop acrossprecision load 722. Additionally or alternatively, in some embodiments,testing circuit can include a way to measure the current through theprecision impedance such as an ammeter.

In operation, referring to FIG. 7A and FIG. 7B, the switch 715 candirect a current to flow from the source element 710, through the switch715, and through the precision load to a reference voltage 742. In someexamples, the current is a steady-state current which does not changeover time. In the example of FIG. 7B, the reference voltage 742 is inelectrical communication with the precision load 732. In some examples,reference voltage 742 comprises a system ground. In some embodiments,the testing circuit 722 can measure the voltage across the precisionload 732 by measuring the voltage at one side of the precision load 732opposite the reference voltage 742 relative to the reference voltage742. In some examples, if the reference voltage 742 comprises a systemground, the testing circuit 722 need not expressly measure the voltageon the system ground 742 side of the precision load 722.

In some examples, the value of the precision load 732 can be known orpredetermined. By measuring the voltage and knowing the value of theprecision load 732, the current flowing through the precision load 732can be determined. For example, for a given voltage V and impedance Z,current I can be found by the equation I=V/Z. In some embodiments, thecontroller 700 determines the current flowing through the precision load732. In some such embodiments, the controller 700 can receive a digitaloutput corresponding to an analog voltage found across the precisionload 732 from an ADC and measure or be programmed with informationregarding the impedance of precision load 732. The controller 700 canuse such information to determine the current flowing through precisionload 732, and therefore the current provided by the source element 710.The calculated current can also be referred to as the measured currentor determined current. In some embodiments, the calculated current,delivered through the precision load 732, can be compared to a desiredcurrent.

FIG. 7C is an alternative testing circuit 724 which can measure thecurrent flowing through a precision load. The testing circuit is incommunication with contact electrode 730 as shown by the dashed lines ofFIG. 7A and FIG. 7C. In operation, referring to the embodiment of FIG.7A and FIG. 7C, the switch can direct a current to flow from the sourceelement 710, through the switch 715, through the precision load 734 ofthe testing circuit 724, and through contact electrode 730. In thisoperation, the current flowing through the precision load 734 can becalculated by measuring the potential difference (e.g. voltage) acrossthe precision load 734.

In some such configurations, no system ground is present for measuringthe potential difference across the precision load 734. In someembodiments, the testing circuit 724 of FIG. 7C can be used to determinethe current provided by the source element 710 while using the currentfrom source element 710 to stimulate cochlear tissue.

As described, in some embodiments, testing circuit is also connected toa controller 700. In the illustrated embodiment of FIG. 7A, thecontroller can interface with testing circuit 720 such that it can beconfigured to determine the amount of electrical current flowing througha precision load in the testing circuit 720. In some embodiments, thecontroller 700 is separate from the testing circuit 720, however, insome examples, at least a portion of the controller is integrated withthe testing circuit such that the testing circuit 720 effectivelydetermines the amount of electrical current flowing through a precisionload.

In the illustrated embodiment of FIG. 7A, the controller 700 can be incommunication with the source element 710 in addition to being incommunication with the testing circuit 720. In such a configuration, thecontroller 700 can control various aspects of the source element 710.For example, the controller 700 can cause a stimulator (e.g. 130 of FIG.1 ) to emit an electrical current from the source element 710. In suchan example, the controller 700 can provide a signal to source element710 such that source element 710 activates and emits an electricalcurrent. The controller 700 can provide a signal to cause source element710 to output a prescribed electrical current.

Current can be directed to testing circuit 720 via switch 715, and thetesting circuit (e.g., the testing circuit 722 of FIG. 7B or 724 of FIG.7C) can be used to measure the current emitted from the source element710. In some embodiments, the controller compares the measured currentto the prescribed current (current that source element 710 is supposedto deliver). For example, source element 710 can be configured todeliver a current of 1 milliamp (e.g. the prescribed current) to thetesting circuit 720 including a precision load. However, due to variousissues and/or inaccuracies as previously discussed, the measured currentflowing through the precision load can be less than or greater than theprescribed 1 milliamp. In the case that the desired current and themeasured current differ, the source element 710 can be adjusted (e.g.calibrated/programmed) such that the current measured at the testingcircuit 722 matches the prescribed current from the controller 700. Insome examples, such calibration can include changing the output currentproduced by the DAC of the source element 710. This can include changingthe LSB's of the DAC to reflect an increase or decrease in the amount ofcurrent desired. Additionally or alternatively, calibration can beperformed in the controller 700 (e.g., the signal processor), whereinthe signal provided from the controller 700 to the source element 710for a given prescribed current is modified. For example, the controller700 can be configured to adjust the LSB's of a signal provided to theDAC for a prescribed current so that the current output from the sourceelement changes for a given prescribed current. In some such examples,the controller 700 can be configured to adjust the signal provided tothe DAC by an offset value, for example, based on the difference betweenthe prescribed current and the measured current. In some such examples,offset values can be associated with differences between the prescribedcurrent and the measured current based on values stored in a lookuptable or based on an equation.

In some embodiments, the source element can include multiple DACs. Insome such examples, the source element comprises a signal generation DACconfigured to generally operate as described herein, and a calibrationDAC in parallel with the signal generation DAC. In some embodiments,controller 700 can be configured to operate the signal generation DAC toprovide a prescribed current and calibrate the applied current byadjusting operation of the calibration DAC (e.g., adjusting a digitalinput thereto in order to adjust the output thereof). Adjustingoperation of the calibration DAC can fine-tune the overall output of thesource element in order to source or sink a calibrated current from thecorresponding contact electrode.

FIG. 7D shows an example source element including a signal generationDAC and a calibration DAC. As shown, source element 712 includes signalgeneration DAC 714 configured to receive a signal (e.g., a digitalsignal) from a controller (e.g., controller 700) and output a signal toa current source/sink 718 that can be configured to source or sink acurrent toward a testing circuit (e.g., 720) and/or contact electrode(e.g., 730) such as described herein based on the signal received fromthe signal generation DAC 714. In some embodiments, source element 712further includes a calibration DAC 716 configured to receive a signalfrom the controller and output a signal to the current source/sink 718.In some examples, the signal from the calibration DAC 716 can be used toadjust the amount of current source/sunk via the source element 712 forcalibration. Additionally, while shown as combining with the signal fromsignal generation DAC 714, the signal from the calibration DAC 716 canbe provided to the current source/sink 718 separately from the signalfrom the signal generation DAC 714.

In general, adjusting the output of the source element, such as done inresponse to a detected discrepancy between a prescribed current and ameasured current, can be done via adjusting operation of the controller700 (e.g., within the signal processor), operation of the source element710 (e.g., operation of a DAC), or a combination thereof.

In some embodiments, the amount of current provided by the sourceelement 710 can be adjusted based on the current measured at the testingcircuit 720 such that the current measured at testing circuit 720matches the prescribed current. By adjusting the amount of currentoutput by the source element 710 such that the measured current matchesthe prescribed current, the accuracy of the signal output by sourceelement 710 can be increased. In some embodiments, a controller 700adjusts the output current of the source element 710 based on thedetermined (e.g. calculated) amount of electrical current which flowsthrough the precision load.

Adjusting (e.g. calibrating) the output current of the source element710 can be repeated any number of times. For example, in someembodiments, after adjusting the output of the source element 710 basedon a measured current, the same source element can be tested again usingthe same prescribed current to confirm that the updated operation isaccurate, or to further refine the operation of the source element 710.Additionally or alternatively, in some examples, the adjustment of theoutput current of the source element 710 is done using a variety ofprescribed current values.

In some examples, the controller can instruct the source element 710 tooutput a first prescribed current. The controller 700 can then comparethe first prescribed current with the corresponding measured currentflowing through the precision impedance of the testing circuit 720. Thecontroller can also instruct the source element 710 to output a secondprescribed current. The controller 700 can then compare the secondprescribed current with the corresponding measured current flowingthrough the precision impedance of the testing circuit 720. From thesetwo comparisons, a line of best fit (e.g. calibration curve) can be usedto adjust the output current of the source element accordingly. In someexamples, more than two prescribed current values can be used to createthe line of best fit for a source element. In some embodiments, a rangeof output currents which encompasses the entire range of the DAC of thesource element can be used to create the line of best fit. By using aline of best fit for calibrating the output current of the sourceelement, the accuracy of the current output from the source elementrelative to the prescribed current across a range of values can beincreased.

After the adjustment of the output current of source element 710 usingtesting circuit 720 has been completed, the switch 715 can be switchedto connect source element 710 to contact electrode 730. Thus, thecalibrated source element 710 can be used with the contact electrode 730to accurately provide prescribed current to the cochlear tissue. In someembodiments, by calibrating source element 710, the charge delivered tothe cochlear tissue by contact electrode can remain neutral can beaccurately controlled to maintain charge neutrality over time.

In some embodiments, adjustment of the source element 710 is done invivo. Additionally, in some embodiments, adjustment of the sourceelement 710 is done after the source element 710 has been calibrated ina factory or other space outside of a patient's body. Alternatively, insome embodiments, adjustment of the source element 710 is done in lieuof any calibration outside of a patient's body. Being able to adjust thesource element 710 in vivo has many benefits over exterior calibrationincluding that the adjustment can be performed at any time withoutremoval of the source element from the patient and that charges can bemore easily balanced, possibly leading to less damage of the cochlearnerve.

In an example operation of the embodiment of FIG. 7A, the source element710 is initially connected to contact electrode 730 through switch 715.After a period of time (or before the first use), it may be desired tocalibrate the amount of output current generated by the source element710 and delivered to the contact electrode 730 to ensure the prescribedamount of current is provided during stimulation. At such a time, thecontroller 700 directs the switch 715 such that the connection betweenthe source element 710 and the contact electrode 730 is severed and aconnection between the source element 710 and the testing circuit 720 ismade. The controller 700 then causes the source element 710 to deliver aprescribed current through the testing circuit 720. The current from thesource element 710 can be directed to a precision load (e.g., 732)within the testing circuit 720. The controller 700 determines the amountof electrical current flowing through the precision load by measuring avoltage across the known impedance of the precision load (e.g., bymeasuring a voltage on one side of the precision load relative to asystem ground). The controller 700 compares the prescribed current withthe determined current (e.g. measured current) and adjusts the operationof the source element 710 so that the measured current matches theprescribed current. After at least one adjustment, the controller 700switches the switch 715 to connect the source element 710 with thecontact electrode 730. The example operation of the embodiment of FIG.7A can be repeated any number of times.

Moving to FIG. 8 , FIG. 8 is a high-level electrical schematic showingcommunications between multiple source elements, multiple switches,multiple contact electrodes, a controller, and a testing circuit. As inthe embodiment of FIG. 7A, each switch of FIG. 8 , which can be a partof switching network, can selectively connect a source element witheither a testing circuit or a corresponding contact electrode. Forexample, in FIG. 8 , a first source element 810 can be in communicationwith a first contact electrode 814 or a testing circuit 860 throughfirst switch 812. Further, a second source element 820 can be incommunication with a second contact electrode 824 or the testing circuit860 through a second switch 822. A controller 850 can control orotherwise manipulate each of the switches to selectively connect eachsource element with each corresponding contact electrode or the testingcircuit 860. In various embodiments, controller 850 can be embodied viaone or more components such as those described with respect tocontroller 700 in FIG. 7 .

In various embodiments, this configuration of elements can be repeated(e.g. consecutively) such that an n number of source elements 830 areselectively connected to an n number of contact electrodes 834 or atesting circuit 860 through an n number of switches 832 as illustratedin FIG. 8 . In some embodiments, the n number of contact electrodes isat least eight. In such embodiments, at least eight source elements andat least eight switches are used with the at least eight contactelectrodes. In some embodiments, ten, twelve, or more contact electrodesare used with a corresponding amount of source elements and switches. Insome examples, the switching network can include elements other than theswitches while in alternative examples, the switching network iscomprised entirely of switches.

Continuing with the example of FIG. 8 , the testing circuit 860 caninclude a precision load, such as shown in the example testing circuitsof FIGS. 7B and 7C. In some examples, testing circuit 860 can include away to measure the voltage across the precision load or otherwisecommunicate the voltage to the controller 850. In some cases, controller850 can measure a voltage across the precision load directly. While theexample of FIG. 8 only includes a single testing circuit 860, multipletesting circuits can be used. Further, in some examples, more than oneprecision load can be used including a more than one previsionimpedances within a single testing circuit. However, the embodiment ofFIG. 8 can be advantageous over other configurations including multipletesting circuits and/or multiple precision loads as it can require fewerresources and take up less physical space.

Further, in the embodiment of FIG. 8 , a controller 850 is incommunication with the plurality of source elements in addition to theplurality of switches. In the illustrated example of FIG. 8 , thecontroller 850 can control each of the source elements and cause them toemit an electrical current. The controller 850 can be in communicationwith testing circuit 860. In such a configuration, the controller 850can control and/or determine different aspects of the testing circuit860. For example, the controller 850 can determine the amount ofelectrical current flowing through a precision load present in thetesting circuit 860. In some embodiments, the controller 850 can use thedetermined amount of current flowing through the testing circuit 860 toadjust a source element such as described herein.

In some embodiments, multiple controllers can be used and, in someembodiments, a controller can be a part/portion of other elements of thecochlear implant system. For example, the controller can be apart/portion of the signal processor (e.g. 120 of FIG. 1 ) and in someembodiments, the controller is the signal processor. Further, in someexamples, the switching network, which includes switches, can also beincluded as part of the signal processor. Moreover, in some example, thetesting circuit can be included as part of the signal processor. In someembodiments, the signal processor includes a switching network and atesting circuit and in some further embodiments, the signal processorincludes a controller in addition to the signal processor and theswitching network. In various embodiments, any combination of theswitching network, the testing circuit, and the controller can beintegrated with the signal processor.

As disclosed with respect to the operation of FIG. 7A, an output currentof a source element can be measured and adjusted (e.g. calibrated)through the use of a testing circuit and a controller. The operation ofFIG. 7A is disclosed relative to a single source element which can beconnected to a single contact electrode. However, the operation of FIG.7A can be repeated for multiple source elements connected to multiplecontact electrodes.

In an example operation of the embodiment of FIG. 8 , a first sourceelement 810 can initially be connected to a first contact electrode 814through a first switch 812. The first source element 810 can deliver anoutput current to the first contact electrode 814. The controller 850can be configured to direct the first switch 812 to sever connectionbetween the first source element 810 and the first contact electrode 814and establish a connection between the first source element 810 and thetesting circuit 860. The controller 860 can cause the first sourceelement 810 to deliver a prescribed output current through the testingcircuit 860, which in some examples flows through a precision loadwithin the testing circuit 860. The controller can determine the amountof electrical current flowing through the precision load, for example,by measuring a voltage across the known impedance of the precision load.The controller 860 can compare the prescribed current from the firstsource element 810 with the determined current, and adjust the outputcurrent of the first source element 810 such that the determined currentmatches the prescribed current. This process can be repeated any numberof times for the first source element 810. Once the first source element810 has been adjusted (e.g. calibrated), the controller can adjust asecond source element 820 connected to a second electrode 824 or thetesting circuit 860 in a similar manner as the first source element 820is adjusted as described above. Adjusting the second source element 820can be done any number of times. Further, the process of adjusting asource element can be repeated n times for each of n number of sourceelements, for example, until all source elements have been adjusted. Insuch a process, each individual source element can be adjusted one afteranother (e.g. consecutively) until all the source elements are adjusted.In some embodiments, eight or more source elements are adjusted tooutput current for eight or more contact electrodes. In someembodiments, ten or twelve source elements can be adjusted.

In an alternative operation of the embodiment of FIG. 8 , the controller850 causes a source element to emit a prescribed electrical current tothe testing circuit 860 and through a precision load. The controllerdetermines the current flowing through the precision load. However,instead of comparing and adjusting the output current of the sourceelement relative to a known current, the controller 850 causes anothersource element to emit a prescribed electrical current to the testingcircuit 860 and through the precision load. The controller determinesthe current flowing through the precision load for the second sourceelement. This process can be repeated until the controller 850 hasdetermined the respective current flowing through the precision load forall the source elements given the prescribed current. In some examples,the respective prescribed current for each of the source elements is thesame during such a process.

Once the controller 850 has the determined currents for each of thesource elements, it can determine characteristics of the determinedcurrents. For example, the controller 850 can determine a first currentflowing through testing circuit 860 from a first source element anddetermine a second current flowing through testing circuit 860 from asecond source element. The controller 850 can then determine variouscharacteristics, such as the minimum amount of electrical current, themaximum amount of electrical current, and the average amount ofelectrical current. Further, this process can be expanded to include nnumber of determined currents flowing through testing circuit 860 froman n number of source elements.

The controller 850 can use the determined characteristics (e.g. averageamount of current) and compare them to the prescribed current. Forexample, an average current of 1.5 milliamps applied to testing circuit860 can be compared to a prescribed current of 1.0 milliamps, adifference of 0.5 milliamps. If the average current is not equal to theprescribed current, the controller can adjust each source element suchthat the average current of all the source elements is the same as theprescribed current. In some embodiments, the controller 850 adjusts allthe source elements the same amount to shift the average amount ofcurrent toward the prescribed current. In some embodiments, adjustingthe output of each source element includes adjusting the LSB of each DACof the source elements by the same amount.

Adjusting all the source elements in example operation of FIG. 8 can beadvantageous as the adjustment is only done in one step instead of on aper-source element basis. However, in some examples, adjusting all thesource elements in the same step can be a first step before thecontroller 850 adjusts each individual source element. For example, allthe source elements can be adjusted the same amount such that theiraverage output current is equal to a desired (e.g. prescribed) current.Each individual source element can be subsequently adjusted such thateach individual output current is equal to a prescribed current. In suchan example, the initial adjusting of all the source elements can puttheir respective output currents closer to the prescribed current, withthe secondary, individual adjusting of each source element putting theoutput currents at the prescribed current. Thus, in some examples, abulk calibration of the output currents of the source elements can beperformed before a fine calibration.

Adjustment of the source elements can be done at any time, however, insome embodiments, adjustment is done at specific times. For example, itcan be advantageous to adjust the source elements soon after thecochlear implant system is implanted into a wearer to ensure accuratestimulation and avoid charge accumulation as soon as possible, limitingany possible damage to the cochlear tissue or implanted components.Additionally or alternatively, calibration can be done after anaudiologist determines specific settings (e.g. setting a transferfunction) of the cochlear implant system after it is implanted. Further,in some embodiments, adjustment can be done periodically, such as atauto-programmed times, or at discrete times, such as when a userinitiates an adjustment (e.g., via a charger or other external componentin communication with the implanted system). Other periods of time forwhen adjustment is performed are contemplated, such as when prescribedby an audiologist, and a person of ordinary skill will understand thatthe present disclosure is not limited to the examples provided.

Moving to FIG. 9 , FIG. 9 shows a schematic illustration of an examplefully implantable cochlear implant system with an external device forprogramming. The illustrated embodiment of FIG. 9 includes a cochlearelectrode 916 in communication with a stimulator 930 and further incommunication with a signal processor 920. The signal processor 920 isalso in communication with a middle ear sensor 910 and an implantablebattery and/or communication module 940. In some examples, the signalprocessor includes a controller. Additionally, implantable batteryand/or communication module 940 can include or otherwise be incommunication with an antenna 942 which is in wireless communicationwith an external device 900. The antenna 942 can be located in theinterior of the wearer, the exterior of the wearer, or a combinationthereof. The antenna 942 can pick up wireless signals from the externaldevice 900 and transmit the wireless signals into the implantablebattery and/or communication module 940. In some examples, the wirelesssignals can include a wireless command. In some such examples, thewireless command can be sent from the external device 900 and reachcontroller (e.g. in signal processor 920).

In operation of the illustrated embodiment, the external device 900 caninitiate and/or perform an adjustment operation such as those describedelsewhere herein. For example, the external device 900 can initiate acontroller to calibrate one or more source elements such as describedelsewhere herein in response to a wireless command. For instance, insome embodiments, external device can initiate an adjustment processthrough implantable battery and/or communication module 940 with adifferent device instructing and/or performing the adjustment process.Additionally or alternatively, in some examples, the external device 900can perform one or calibration steps. For instance, in some examples,external device 900 can designate a prescribed current to be providedfrom a source element and receive information indicative of theresulting current received at a testing circuit. The external device 900can be configured to adjust the output of the source element based onthe prescribed current and the received information indicative of theresulting current. For example, in some embodiments, external device 900can communicate to implantable battery and/or communication module 940various commands and/or values in order to adjust the stimulator 930 tooutput a current which is the same as the prescribed current. In otherembodiments

Additionally or alternatively, in some embodiments, adjustments can bedone manually. For example, an audiologist can connect to a portion ofthe cochlear implant system (e.g. programmer 100 of FIG. 1 ) andmanually control aspects of the adjustment process (e.g. currentlevels). In some embodiments, manual adjustments can be done remotelyusing an external device 900. In some examples, adjustment is done forone or more electrodes and in some examples, adjustment is done for oneor more magnitudes of prescribed current.

FIG. 10 is an example adjustment (e.g. calibration) process using acontroller for a cochlear implant system. Beginning with step 1000, thecontroller positions a source element into communication with a testingcircuit. In some embodiments, this step includes switching a switch froma position in which the source element is in communication with acontact electrode to a different position in which the source element isin communication with a testing circuit. Moving to step 1010, thecontroller applies electrical current to the testing circuit. In someembodiments, this step includes causing a stimulator to emit anelectrical current from the source element to the testing circuit.Moving to step 1020, the controller determines the amount of currentapplied to the testing circuit. In some embodiments, this step caninclude measuring a voltage across a precision load, for example, havinga known impedance, within the testing circuit and calculating the amountof current applied to the testing circuit. As described herein, in someexamples, this includes measuring a single voltage relative to a systemground. Moving to step 1030, the controller determines if the amount ofcurrent applied to the testing circuit is the same as the prescribedcurrent. In some embodiments, the controller further determines thedifference between the current applied to the testing circuit and theprescribed current. If the comparison of step 1030 results in a logicalno (e.g. the amount of current applied to testing circuit does not equalthe prescribed current) the controller can adjust the output of thesource element as in step 1040. In some embodiments, the controlleradjusts the output current of the source element such that it is thesame as the prescribed current.

In the illustrated example, if the amount of current applied to testingcircuit does equal the prescribed current, or if the output of thesource element has been adjusted as in step 1040, the process moves tostep 1050. In step 1050, the controller can determine if all the sourceelements have been calibrated. If all the source elements have not beencalibrated, the process starts over with step 1000, comprisingpositioning a next source element into communication with the testingcircuit. However, if all the source elements have been calibrated, theprocess can be finished with step 1060 wherein the calibration iscomplete.

It will be appreciated that, while in some embodiments, the process ofFIG. 10 can be carried out via a controller, the controller need notperform each step shown in FIG. 10 . For instance, in some suchembodiments, the controller need not literally determine a binary orlogical “yes or no” answer in steps 1030 and 1050. For instance, in someexamples, the controller can be configured to adjust an output of asource element based on a difference between a measured and prescribedcurrent. In some such examples, if the measured current is equal to theprescribed current, an adjustment step can include an “adjustment” equalto zero rather than determining a binary “yes” that the prescribed andmeasured current are equal and skipping the adjustment step.

Moving to FIG. 11 , FIG. 11 is an alternative example adjustment (e.g.calibration) process (e.g. method) using a controller for the cochlearimplant system. Beginning with step 1100, the controller positions asource element into communication with a testing circuit. In someembodiments, this step includes switching a switch from a position inwhich the source element is in communication with a contact electrode toa different position in which the source element is in communicationwith a testing circuit. Moving to step 1110, the controller applieselectrical current to the testing circuit. In some embodiments, thisstep includes causing a stimulator to emit an electrical current fromthe source element to the testing circuit. Moving to step 1120, thecontroller determines the amount of current applied to the testingcircuit. Similar to described elsewhere herein, in some embodiments,this step can include measuring a voltage across a precision load havinga known impedance within the testing circuit and calculating the amountof current applied to the testing circuit.

Moving to step 1130, the controller can determine if all the sourceelements have been tested. If all the source elements have not beentested, the process starts over with step 1100, positioning a nextsource element into communication with the testing circuit. However, ifall the source elements have been tested, the adjustment process cancontinue with step 1140. In step 1140, the controller can determine anaverage applied current among the source elements. In some embodiments,this step includes determining an average current flowing through aprecision load of the testing circuit among all the source elements.Moving to step 1150, the controller can compare the average appliedcurrent among the sources to a prescribed current. In the case that theaverage applied current is not the same as the prescribed current, thecontroller can perform step 1160, in which the controller adjusts theoutput of each source element, for example, so that the average currentequals the prescribed current.

In some embodiments, after the controller adjusts the output of eachsource element, or if the average current was equal to the prescribedcurrent, the controller can perform step 1170, wherein the controlleradjusts (e.g. calibrates) the individual source elements. In someembodiments, this subsequent adjustment (e.g. calibration) is done inaccordance with the process outlined in FIG. 10 . Such individual sourcecalibration can be used to fine tune each source element after bulkcalibrating the source elements by adjusting their outputs based on theaverage measured current.

In some examples, after the controller adjusts the output of each sourceelement in step 1160, the process can start over with step 1100 whereinthe controller positions the next source element into communication withthe testing circuit. For example, the process can include testing eachsource element, averaging the resulting currents, and adjusting eachsource element to shift the average applied current toward theprescribed current multiple times, for example, prior to calibrating theindividual source elements in step 1170.

Similar to described with respect to FIG. 10 , in some examples, theprocess of FIG. 11 can be performed by a system controller. However, insome such examples, the controller need not determine a binary/logical“yes” or “no” at steps 1130 or 1150.

Various non-limiting embodiments have been described. These and othersare within the scope of the following claims.

1. A cochlear implant system comprising: a cochlear electrode comprisinga plurality of contact electrodes; a stimulator in electricalcommunication with the cochlear electrode, the stimulator including aplurality of source elements, each of the plurality of source elementsbeing in electrical communication with a corresponding one of theplurality of contact electrodes of the cochlear electrode; an inputsource configured to receive a stimulus signal and generate an inputsignal based on the received stimulus signal; a signal processor incommunication with the stimulator and the input source, the signalprocessor being programmed with a transfer function and being configuredto receive the input signal from the input source and output astimulation signal to the stimulator based on the received input signaland the transfer function; a testing circuit; a switching networkconfigured to selectively place each of the plurality of source elementsinto electrical communication with the testing circuit; and a controllerin communication with the stimulator, the testing circuit, and theswitching network and configured to: control the switching network toplace one of the plurality of source elements into communication withthe testing circuit; and (a) cause the stimulator to emit an electricalcurrent from the one of the plurality of source elements incommunication with the testing circuit; (b) determine an amount ofelectrical current emitted from the one of the plurality of sourceelements via the testing circuit; and (c) adjust the output of the oneof the plurality of source elements based on the determined amount ofelectrical current.
 2. The cochlear implant system of claim 1, whereinthe adjusting the output of the one of the plurality of source elementsbased on the determined amount of electrical current comprises comparingthe determined amount of electrical current to a desired amount ofelectrical current and adjusting the output of the source element basedon the comparison.
 3. The cochlear implant system of claim 1, whereinthe testing circuit comprises a precision load such that, when thestimulator emits the electrical current from the one of the plurality ofsource elements in communication with the testing circuit the electricalcurrent flows through the precision load.
 4. The cochlear implant systemof claim 3, wherein the determining the amount of electrical currentemitted from the one of the plurality of source elements comprisesmeasuring a voltage across the precision load.
 5. The cochlear implantsystem of claim 4, wherein the testing circuit comprises an analog todigital converter (ADC), and wherein the measuring the voltage acrossthe precision load comprises receiving an output from the ADCcorresponding to the voltage across the precision load.
 6. The cochlearimplant system of claim 5, wherein the testing circuit further comprisesa reference voltage in electrical communication with the precision loadsuch that the electrical current from the stimulator flows through theprecision load and then to the reference voltage.
 7. The cochlearimplant system of claim 6, wherein the measuring the voltage across theprecision load comprises measuring the voltage at one side of theprecision load opposite the reference voltage.
 8. The cochlear implantsystem of claim 1, wherein the controller is configured to: control theswitching network to consecutively place each of the plurality of sourceelements into communication with the testing circuit; and perform steps(a), (b), and (c) for each of the plurality of source elements.
 9. Thecochlear implant system of claim 1, wherein each of the plurality ofsource elements comprises a corresponding digital to analog converter(DAC) configured to receive a digital input signal and output an analogsignal in response to the digital input signal causing a current to beemitted from the corresponding source element.
 10. The cochlear implantsystem of claim 9, wherein each DAC is configured to output a current inresponse to the received digital input signal.
 11. The cochlear implantsystem of claim 9, wherein each DAC is configured to output a voltage inresponse to the received digital input signal, and wherein the voltagecauses a corresponding current to be output from the correspondingcurrent source.
 12. The cochlear implant system of claim 9, wherein:each of the plurality of source elements comprises a signal generationDAC and a calibration DAC arranged in parallel with the signalgeneration DAC; the causing the stimulator to emit the electricalcurrent comprises emitting the electrical current via the signalgeneration DAC; and the adjusting the output of the one of the pluralityof source elements based on the determined amount of electrical currentcomprises adjusting operation of the calibration DAC.
 13. The cochlearimplant system of claim 9, wherein the DAC of each of the plurality ofsource elements comprises at least six bits of precision.
 14. Thecochlear implant system of claim 9, wherein the controller is configuredto: control the switching network to consecutively place each of theplurality of source elements into communication with the testingcircuit; for each of the plurality of source elements: provide a firstdigital signal to the corresponding DAC, the first digital signalcorresponding to a first predetermined current level; and determine theresulting current flowing from the source element; determine an averageamount of current flowing from each of the plurality of source elements;compare the determined average amount of current to the firstpredetermined current level; and adjust each of the DACs by the sameamount to shift the average amount of current toward the firstpredetermined current level.
 15. The cochlear implant system of claim 1,wherein: the controller is configured to perform steps (a) and (b) foreach of a plurality of electrical current values; and wherein step (c)comprises determining a best fit adjustment across the plurality ofelectrical current values and adjusting the output of the source elementaccording to the determined best fit adjustment.
 16. The cochlearimplant system of claim 1, wherein each of the plurality of sourceelements is capable of sourcing and sinking current.
 17. The cochlearimplant system of claim 1, wherein the cochlear electrode comprises atleast eight contact electrodes.
 18. The cochlear implant system of claim1, further comprising an implantable battery and/or communication modulein communication with the signal processor and being configured toprovide electrical power to the signal processor; and wherein thecontroller is the signal processor.
 19. The cochlear implant system ofclaim 1, further comprising an external component, and wherein thecontroller is configured to perform steps (a)-(c) in response to awireless command received from the external component.
 20. The cochlearimplant system of claim 1, wherein the input source comprises a middleear sensor. 21-28. (canceled)